The present invention relates to a novel visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for an imaging device, and in particular to a visual displacement sensor which can freely define the field of view of the imaging device serving as an object for extracting measurement point coordinates.
The inventors of this application previously proposed a novel visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for an imaging device.
According to such a visual line sensor, several advantages can be gained because a line beam is used as the measurement light, the displacement of a measurement object point can be measured as a line instead of a series of dots.
A visual displacement sensor of this type comprises, as essential elements, a light emitting device (such as a laser diode) for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device (such as a two-dimensional CCD, for monitoring the object to be measured, on which the line beam is impinged, from a different angle, measurement point coordinate determining means for determining a measurement point coordinate according to a reflected line beam light image in an image captured by the two-dimensional imaging device, and displacement measuring means for measuring a desired displacement according to the determined measurement point coordinate.
If the measurement condition is ideal, the number of reflected line beam light image that appears in the, field of view of the two-dimensional imaging device should agree with the expected number. In other words, if the measurement object consists of an opaque member and has no steps on its surface, there should be only one reflected line beam light image in the field of view of the two-dimensional imaging device. When the measurement object consists of a transparent member such as a glass plate or when the measurement object consists of an opaque member but has a step or the like on its surface, the number of the reflected line beam light images that appear in the field of view of the two-dimensional imaging device should agree with the expected number which is determined by the number of laminated glass plates and/or the number of steps.
The displace measurement algorithm for measuring the desired displacement according to the determined measurement point coordinate can function properly and measure the desired displacement only when the sensor is placed under an expected measurement condition. In other words, if the number of reflected line beam light images in the field of view of the two-dimensional imaging device docs not agree with the expected number, the measurement of the desired displacement would run into a serious difficulty.
Also, the measurement point coordinate determining algorithm for determining a measurement point coordinate according to the reflected line beam light image in the image that is captured by a two-dimensional imaging device can function properly only when the sensor is placed under an expected measurement condition. In other words, if the gradation level of the reflected line beam light image does not fall in a prescribed range, the determination of the measurement point coordinate would run into a serious difficulty.
Therefore, according to a visual displacement sensor of this kind, if a spurious reflected line beam light image appears in the field of view of the two-dimensional imaging device due to an improper measurement condition, and the number of measurement point coordinates exceeds the expected number, the displacement measurement algorithm may fail to measure the desired displacement in a normal fashion.
Furthermore, according to a visual displacement sensor of this kind, if the measurement object consists of a transparent member having metallic film having a high reflectivity formed over the back surface thereof as is the case with a glass plate of a CRT or an LCD panel, because in spite of the automatic gradation adjustment function the gradation level for each and every one of the reflected line beam light image that appear in the field of view of the two-dimensional imaging device in a mutually spaced relationship in the direction of displacement measurement may fail to fall within a prescribed range, the measurement point coordinate determining algorithm incorporated in the sensor may fail to determine the measurement coordinates, and the desired displacement the measurement point coordinate may fail to be determined in a normal fashion as a result as far as those reflected line beam light image having gradation levels falling out of the prescribed range are concerned.
Additionally, according to a visual displacement sensor of this kind, when measuring a measurement object consisting of a step by impinging a line beam across the step, if there is a large difference in reflectivity between the upper and lower surfaces of the step, in spite of the operation of the automatic gradation adjustment function, it becomes impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction perpendicular to the direction of displacement measurement within a prescribed range over the entire reflected line beam light image. Therefore, the part of the reflected line beam light image having a gradation level falling out of the prescribed range prevents the measurement point coordinate determining algorithm incorporated in the sensor from properly determining the measurement point coordinate, and the desired displacement fails to be measured in a normal fashion as a result.
The present invention was made in view of such problems of the visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for a measurement imaging device, and its primary object is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even when a spurious reflective line beam image appears within the field of view of the two-dimensional imaging device due to an improper measurement condition, and the number of measurement point coordinates exceeds an expected number.
Another object of the present invention is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consists of a transparent plate having metallic film having a high reflectivity level formed over its back surface as is the case with the glass plate of a CRT or an LCD panel.
Yet another object of the present invention is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction perpendicular to the direction of displacement measurement within a prescribed range over the entire reflected line beam light image in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consisting of a step is measured by impinging a line beam across the step and there is a large difference in reflectivity between the upper and lower surfaces of the step.
Yet another object of the present invention is to provide a visual displacement sensor which can continue to measure the thickness of a glass plate and the size of a step in a stable manner even when the position of the glass plate for thickness measurement changes in the direction of the thickness and the position of the measurement object for step size measurement moves in the direction of the length of the reflected image of the line beam that is impinged on the measurement object.
Yet another object of the present invention is to provide a visual displacement sensor which can notify the operator the cause in an accurate manner through guide display even when the measurement is rendered impossible due to various reasons such as the presence of external light, the difference in reflectivity between the front and back surfaces of a transparent member, and the difference in reflectivity between the upper and lower surfaces of a step.
Other objects of the advantages of the present invention will become apparent for a person skilled in the art from the following description.
According to an aspect of the present invention, the visual displacement sensor of the present invention comprises a light emitting device for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device for monitoring the object to be measured, on which the line beam is impinged, from a different angle, measurement object range defining means for defining one or more than one measurement object range within a field of view of the two-dimensional imaging device, measurement point coordinate determining means for determining one or more than one measurement point coordinate contained in the defined measurement object range according to an image captured by the two-dimensional imaging device, and displacement measuring means for measuring a desired displacement according to the determined one or more than one measurement point coordinate.
According to this structure, even when a spurious reflective line beam image appears within the field of view of the two-dimensional imaging device due to an improper measurement condition such as external light, and the number of measurement point coordinates exceeds an expected number, a desired displacement can be brought back into a measurable state by using a displacement measurement algorithm incorporated in the sensor simply by the operator defining a measurement object range so as to exclude the light image due to the external light.
The one or more than one measurement object range defined by the measurement object range defining means may be defined with respect to a direction of displace measurement in the field of view of the two-dimensional imaging device, a direction perpendicular to a direction of displace measurement in the field of view of the two-dimensional imaging device, or both a direction of displace measurement and a direction perpendicular to a direction of displace measurement in the field of view of the two-dimensional imaging device.
According to a preferred embodiment of the present invention, the measurement point coordinate determining means determines one or more than one measurement point according to an image extracted from the image captured by the two-dimensional imaging device by masking the area other than the defined one or more than one measurement object range.
According to a preferred embodiment of the present invention, the measurement point coordinate determining means provisionally determines one or more than one measurement point according to an entire image captured by the two-dimensional imaging device, and finally determines one or more than one measurement point by comparing the provisionally determined one or more than one measurement point with a counterpart in the defined one or more than one measurement object range.
According to a preferred embodiment of the present invention, the sensor additionally comprises monitor image editing means for displaying information on a state of the raw image captured by the two-dimensional imaging device on the image monitor screen. In this case, the information on a state of the raw image may comprise the raw image itself and/or a line bright waveform corresponding to the raw image.
According to a preferred embodiment of the present invention, the sensor additionally comprises monitor image editing means for displaying information on a state of the masked image extracted from the raw image captured by the two-dimensional imaging device by masking a part thereof other than the defined measurement object range on the image monitor screen. In this case, the information on a state of the masked image may comprise the masked image itself and/or a line bright waveform corresponding to the masked image.
According to a preferred embodiment of the present invention, the sensor additionally comprises monitor image editing means for displaying information corresponding to the measurement object range defined in the field of view of the two-dimensional imaging device on the image monitor screen. In this case, the information corresponding to the measurement object range may consist of a value indicating a boundary and/or boundary position of the measurement object range on the raw image or masked image.
According to a preferred embodiment of the present invention, the sensor additionally comprises monitor image editing means for displaying information corresponding to the measurement point coordinate determined in the field of view of the two-dimensional imaging device on the image monitor screen. In this case, the information corresponding to the measurement point coordinate may consist of a value indicating a measurement point coordinate position and/or measurement point coordinate on the raw image or masked image.
According to a preferred embodiment of the present invention, the sensor additionally comprises a graphical user interface (GUI) for enabling the defining, changing and canceling of the measurement object range in the field of view of the two-dimensional imaging device with an operation on the image monitor screen.
According to another aspect of the present invention, the visual displacement sensor of the present invention comprises a light emitting device for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device for monitoring the object to be measured on which the line beam is impinged from a different angle, measurement object range defining means for defining more than one measurement object range having a designated position and length in the direction of displacement measurement within a field of view of the two-dimensional imaging device, measurement point coordinate determining means having a gradation adjusting function for determining one or more than one measurement point coordinate contained in the defined measurement object range according to an image captured by the two-dimensional imaging device and adjusting at least one line beam light image gradation if the corresponding measurement object range contains one or more line beam light image, and displacement measuring means for measuring a desired displacement according to the determined one or more than one measurement point coordinate.
According to this structure, even when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consists of a transparent plate having metallic film having a high reflectivity level formed over its back surface as is the case with the glass plate of a CRT or an LCD panel, simply by the operator defining measurement object ranges independently for the individual reflected line beam light images, the measurement point coordinate can be determined even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range by using a displacement measurement algorithm incorporated in the sensor, and a desired displacement can be brought back into a measurable state as a result.
According to a preferred embodiment of the present invention, the sensor further comprises a range automatic tracking means for tracking a change in a measurement displacement with respect to a reference surface of a measurement object and moving at least one measurement object range in a direction of displacement measurement direction.
According to yet another aspect of the present invention, the visual displacement sensor of the present invention comprises a light emitting device for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device for monitoring the object to be measured on which the line beam is impinged from a different angle, measurement object range defining means for defining more than one measurement object range having a designated position and length in a direction perpendicular to the direction of displacement measurement within a field of view of the two-dimensional imaging device, measurement point coordinate determining means having a gradation adjusting function for determining one or more than one measurement point coordinate contained in the defined measurement object range according to an image captured by the two-dimensional imaging device and adjusting at least one line beam light image gradation if the corresponding measurement object range contains one or more line beam light image, and displacement measuring means for measuring a desired displacement according to the determined one or more than one measurement point coordinate.
According to this structure, even when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction perpendicular to the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consisting of a step is measured by impinging a line beam across the step and there is a large difference in reflectivity between the upper and lower surfaces of the step, simply by the operator defining measurement object ranges separately for the upper and lower surfaces of the step, the measurement point coordinate can be determined even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range by using a displacement measurement algorithm incorporated in the sensor, and a desired displacement can be brought back into a measurable state as a result.
According to yet another aspect of the present invention, the visual displacement sensor of the present invention comprises a light emitting device for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device for monitoring the object to be measured on which the line beam is impinged from a different angle, measurement object range defining means for defining more than one measurement object range having a designated position and length in both the direction of displacement measurement and a direction perpendicular to the direction of displacement measurement with a two-dimensional expanse within a field of view of the two-dimensional imaging device, measurement point coordinate determining means having a gradation adjusting function for determining one or more than one measurement point coordinate by taking into account the defined measurement object range according to an image captured by the two-dimensional imaging device and adjusting the gradation of each line beam light image, and displacement measuring means for measuring a desired displacement according to the determined one or more than one measurement point coordinate.
According to this structure, even when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consists of a transparent plate having metallic film having a high reflectivity level formed over its back surface as is the case with the glass plate of a CRT or an LCD panel, simply by the operator defining measurement object ranges independently for the individual reflected line beam light images, the measurement point coordinate can be determined even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range by using a displacement measurement algorithm incorporated in the sensor, and a desired displacement can be brought back into a measurable state as a result. Additionally, according to this structure, even when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction perpendicular to the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consisting of a step is measured by impinging a line beam across the step and there is a large difference in reflectivity between the upper and lower surfaces of the step, simply by the operator defining measurement object ranges separately for the upper and lower surfaces of the step, the measurement point coordinate can be determined even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range by using a displacement measurement algorithm incorporated in the sensor, and a desired displacement can be brought back into a measurable state as a result.
According to yet another aspect of the present invention, the visual displacement sensor of the present invention comprises a light emitting device for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device for monitoring the object to be measured, on which the line beam is impinged, from a different angle, measurement object range defining means for defining one or more than one measurement object range within a field of view of the two-dimensional imaging device, measurement point coordinate determining means for determining one or more than one measurement point coordinate contained in the defined measurement object range according to an image captured by the two-dimensional imaging device, displacement measuring means for measuring a desired displacement according to the determined one or more than one measurement point coordinate, and defined range moving means for moving at least one of the one or more than one measurement object range that are defined according to information derived from an image captured by the two-dimensional imaging device.
According to a preferred embodiment of the present invention, when it its determined that the reference surface has moved according to the image captured by the two-dimensional imaging device, the defined range moving means moves the measurement object range corresponding to a surface forming a pair with the reference surface in the direction of displacement measurement following the movement of the reference surface.
According to a preferred embodiment of the present invention, the determination that the reference surface has moved is made in response to a change in the displacement measured by using the measurement object range defined in advance according to the reference surface.
According to a preferred embodiment of the present invention, when it its determined that a boundary line of a step on the measurement object has moved according to the image captured by the two-dimensional imaging device, the defined range moving means moves a pair of measurement object ranges defined on either side of the step boundary line in a direction perpendicular to the direction of displacement measurement following the movement of the step boundary line.
According to a preferred embodiment of the present invention, the determination that the step boundary line has moved is made in response to a movement of an intersection between the measured displacement along the length of the line beam and a prescribed displacement threshold value in a direction perpendicular to the direction of displacement measurement.
In this case, the prescribed displacement threshold value may be defined so as to follow the measured value of the reference step surface forming the step.
According to yet another aspect of the present invention, the visual displacement sensor of the present invention comprises test measurement means for measuring a thickness of a transparent member having a known thickness as a test, thickness teaching means for teaching the thickness of the transparent member, and computational calibration means for calibrating an arithmetic equation for computing the thickness of the transparent member according to the thickness measured as a test and the taught thickness.
According to a preferred embodiment of the present invention, the sensor further comprises monitor image editing means for displaying operation guide information required for measuring the thickness as a test or for teaching the thickness on an image monitor screen in an interactive manner.
According to this structure, the calibration for the measurement of the thickness of a transparent member by using a displacement sensor of this kind can be substantially simplified for the user.